redis源码从main开始9

本章再来看几个常见命令，分别为dbsize、exists、del命令

1.返回库键总数
dbsize
// 127.0.0.1:6379> dbsize
// (integer) 11
//返回db->ht[0].used+db->ht[1].used
void dbsizeCommand(redisClient *c) {
    addReplyLongLong(c,dictSize(c->db->dict));
}
#define dictSize(d) ((d)->ht[0].used+(d)->ht[1].used)



2.键是否存在
exists
// 127.0.0.1:6379> exists aaa 
// (integer) 1
// 先检查是否过期,再检查是否存在

void existsCommand(redisClient *c) {
    expireIfNeeded(c->db,c->argv[1]);
    if (dbExists(c->db,c->argv[1])) {
        addReply(c, shared.cone);
    } else {
        addReply(c, shared.czero);
    }
}
int dbExists(redisDb *db, robj *key) {
    return dictFind(db->dict,key->ptr) != NULL;
}


/*
计算哈希值,判断是否存在
 */
dictEntry *dictFind(dict *d, const void *key)
{
    dictEntry *he;
    unsigned int h, idx, table;

    if (d->ht[0].size == 0) return NULL; /* We don't have a table at all */
    if (dictIsRehashing(d)) _dictRehashStep(d);

    h = dictHashKey(d, key);
    for (table = 0; table <= 1; table++) {
        idx = h & d->ht[table].sizemask;
        he = d->ht[table].table[idx];
        while(he) {
            if (dictCompareKeys(d, key, he->key))
                return he;
            he = he->next;
        }
        if (!dictIsRehashing(d)) return NULL;
    }
    return NULL;
}


3.删除键
del key [key …]
// 127.0.0.1:6379> del aaa bbb
// (integer) 2

//先检查过期,在判断删除
void delCommand(redisClient *c) {
    int deleted = 0, j;
    for (j = 1; j < c->argc; j++) {
        expireIfNeeded(c->db,c->argv[j]);
        if (dbDelete(c->db,c->argv[j])) {
            signalModifiedKey(c->db,c->argv[j]);
            notifyKeyspaceEvent(REDIS_NOTIFY_GENERIC,
                "del",c->argv[j],c->db->id);
            server.dirty++;
            deleted++;
        }
    }
    addReplyLongLong(c,deleted);
}


int dbDelete(redisDb *db, robj *key) {
    if (dictSize(db->expires) > 0) dictDelete(db->expires,key->ptr);
    if (dictDelete(db->dict,key->ptr) == DICT_OK) {
        if (server.cluster_enabled) slotToKeyDel(key);
        return 1;
    } else {
        return 0;
    }
}

int dictDelete(dict *ht, const void *key) {
    return dictGenericDelete(ht,key,0);
}

// 与dictFind类似,找到后删除
static int dictGenericDelete(dict *d, const void *key, int nofree)
{
    unsigned int h, idx;
    dictEntry *he, *prevHe;
    int table;
    if (d->ht[0].size == 0) return DICT_ERR;
    if (dictIsRehashing(d)) _dictRehashStep(d);
    h = dictHashKey(d, key);
    for (table = 0; table <= 1; table++) {
        idx = h & d->ht[table].sizemask;
        he = d->ht[table].table[idx];
        prevHe = NULL;
        while(he) {
            if (dictCompareKeys(d, key, he->key)) {
                if (prevHe)
                    prevHe->next = he->next; // 如果有上一个节点,那么上一个节点等于下一个节点
                else
                    d->ht[table].table[idx] = he->next; // 第一个节点就是要删除的,记录从下一个节点开始
                if (!nofree) {
                    dictFreeKey(d, he);
                    dictFreeVal(d, he);
                }
                zfree(he);
                d->ht[table].used--;
                return DICT_OK;
            }

            prevHe = he;
            he = he->next;
        }
        if (!dictIsRehashing(d)) break;
    }
    return DICT_ERR;
}

基于版本3.0.0版本,点击下载https://download.redis.io/releases/redis-3.0.0.tar.gz

本文地址，https://www.ccagml.com/?p=398